Morning,I have a seaward primetest Primetest PA 100 and need to test 110v transformers.I have the neccesary leads, am attemptig to test it as a class one appliance though it obviously doens't have any exposed metal casing and it is earthed. I've even tried a test on the class 2 & cable functions!I cannot get a result though I know the units to be fiunctional (even tried on a hired unit which "should" be PA tested before hire).Any help greatly appreciated, especially specific to the PA 100.

I'm not familiar with the PAT100 but would visually inspect, test Earth Continuity between 13A plug and 110V output socket(s) earth (the larger diameter connection of the 3) , a 500V insulation test on the 230V side only and a function test using a previously tested 110V appliance.

You don't mention if this is a 230v to 110v transformer, or a 110v isolation transformer, etc? To check earth bond I keep an earth pin (in fact x2 16A and 32A) from old broken connectors in my toolkit and test each socket accordingly (remember to remove the pin after testing). You can also check insulation resistance on the primary side of the transformer. You can also plug a known good 110v item into each output socket and do some leakage/load tests subject to the class of item plugged in. Cable type tests will not be suitable on a transformer.